#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int count(int a)
{
	if (a < 3)
		return 1;
	return count(a - 1) + count(a - 2);
}
int main()
{
	int a;
	scanf("%d", &a);
	int num = count(a);
	printf("%d", num);
}
